Bad air travels in, out of Valley

STOCKTON - Breathe deeply on a windy day and you might inhale traces of exhaust from a stop-and-go traffic jam on the Bay Bridge.

Alex Breitler

STOCKTON - Breathe deeply on a windy day and you might inhale traces of exhaust from a stop-and-go traffic jam on the Bay Bridge.

Fire up your gas-powered lawn mower, however, and you generate your own pollutants that could contribute to haze hanging over Yosemite National Park.

The San Joaquin Valley is famous for its bad air. Now Valley air cops want to better understand how much of the nasty stuff blows in from out of town.

State reports show, however, that just as the Valley grudgingly receives pollution from San Francisco and Sacramento, so too does it send its own hazardous air to regions across the state, from the Pacific coast to the High Sierra.

"Air pollution does not respect county boundaries," said Lakhmir Grewal, air pollution control officer for Calaveras County.

A series of wildfires like those burning in Southern California spurred this latest study, approved last month by the Valley's Air Pollution Control District.

The latest fires, initially fueled by Santa Ana winds, blew most of the smoke out into the ocean and up the coast. Shifting winds late last week began sending that smoke north, into the Valley.

Events such as this make officials wonder how much pollution we get from the southern part of the state, or other regions, every day.

Air is like a river of water as it flows through basins and over mountain passes, said district air quality specialist David Nunes. It picks up whatever it encounters along the way.

Learning about imported pollution would be helpful, he said, because the district is struggling to meet federal ozone standards. This summer it was criticized for postponing compliance until 2023, saying it had no way to meet the target on time.

Ozone, a precursor to smog, forms when various pollutants combine and cook under the hot Valley sun. The Valley's bowl-like shape traps the air and makes matters worse.

With a better understanding of how many ozone-forming pollutants come from other areas, officials say they could work with other air districts to reduce upwind emissions.

Sounds nice, but the district should put time into solving its own problems, said Kathryn Phillips, who follows air quality issues for the conservation group Environmental Defense.

"We've got to take some responsibility for what we're doing," Phillips said.

That could include enforcement of existing regulations, and incentives to reduce pollution from both stationary sources like farms and factories, and mobile sources like automobiles, she said.

The California Air Resources Board says the Valley is polluted by just two outside areas, the Bay Area and Sacramento.

Delta breezes carry Bay Area pollution into the north Valley, where it mixes with Stockton-area emissions and heads south toward Fresno.

The same winds blow a mix of Bay Area and Valley pollution into the foothills and east over the Sierras.

Winds in the south Valley push pollution into the Mojave Desert, and sometimes west to the Central Coast.

Lightly-populated Calaveras County's bad air days can be blamed largely on upwind areas such as the Valley and Bay Area, said Grewal, the county's air pollution officer.

What's needed, he said, are consistent air pollution prevention programs in all areas.

"We shall comply (with air quality standards) as soon as the San Joaquin Valley does," he said. "It's a very fair statement."